• 한국결정성장학회지
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• 제14권2호
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• pp.73-77
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• 2004

수열처리법을 이용하여 저품위의 잠비아산 천연 자수정의 색상 개선을 행하였다. 수열처리 조건은 다음과 같다. 즉, 수열용매 6M-HCI, 반응온도 $300^{\circ}C$, 반응시간 30시간, 충진율 40%이었다. 이와 같은 조건에서 고품질 적자색의 자수정이 얻어졌다. ICP/AES 결과로부터 색 향상은 잠비아산 자수정의 내부에 존재하는 Fe 원소의 함량이 영향을 미치는 것을 알았다. 또한 UV-VIS-NIR분석결과 처리전 잠비아산 수정과 비교해 550nm 흡수피크가 작아짐을 볼 수 있었다. 본 연구의 결과는 수열처리가 잠비아산 자수정의 상업적인 가치 증가에 있어서 적합한 방법이었다.

• 한국세라믹학회지
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• 제39권3호
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• pp.308-314
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• 2002

$ZrOCl_2{\cdot}8H_2O$ 수용액과 $NH_4OH$ 수용액을 반응시켜 얻은 지르코니아 수화물을 반응조건으로 100∼250$^{\circ}$C, 1∼48시간과 1, 5 M NaOH 수용액에서 수열합성하여 결정형 나노크기의 지르코니아 분말을 제조하였다. 수열합성 온도가 낮을 경우 구형의 정방정상 나노입자가 합성되었으며, 합성온도가 증가하면서 입자크기의 증가 및 입자모양도 막대상으로 변하면서 결정상도 단사정상을 나타내었다. NaOH 용액의 몰 농도가 증가함에 따라 합성된 입자의 폭과 길가 크며 장단축비는 감소하였다. 반면에 NaOH 용액의 농도가 낮을 경우 입자 길이가 폭에 비해 상대적으로 크고, 이에 따라 장단축비가 큰 막대상 입자가 합성되었다.

• 한국세라믹학회지
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• 제31권11호
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• pp.1401-1413
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• 1994

The synthesis of kaolinite mineral from domestic diatomite for silica resource, commercial vailable gibbsite or alumina for alumina resource were made under various hydrothermal treatment, and the sythetic effect of acidic mineralizers, temperature treatment with time duration, particle size of alumina on formation of kaolinite mineral and the plastic properties of synthesized kaolinite were investigated. The various acidic mineralizers which are HCl, HNO3, H2SO4 and Oxalic acid were employed for hydrothermal reaction in the range of 0.01 mol/ι to 2 mol/ι concentration of each mineralizers. It was found that HCl in the level of 1 mol/ι solution produced highly yields of well-crystallized and platy form kaolinite mineral and gave the most effective extraction of iron oxide, compared to that of others, that HNO3 produced highly yield of kaolinite but lower extraction of iron oxide, that H2SO4 produced low yield of kaolinite and formed alunite mineral, and that oxialic acid formed spherical crystalline kaolinite and gave low extraction of iron oxide. Moreover, it showed that kaolinite minerals were well synthesized in a wide range of less than 2 mol/ι acids, but were poorly synthesized at more than 2 mol/ι acids. However, boehmite and kaolinite were coexistently formed in the temperature range of 18$0^{\circ}C$ and 20$0^{\circ}C$ when the calcined diatomite and gibbsite were involved. The well-ordered kaolinite mineral as a platy form was highly synthesized in the temperature range of 220 and 24$0^{\circ}C$, when the same marterials as above were used with treatment of 1 mol/ι HCl solution. The results also revealed that the size of crystalline platy form kaolinite, synthesized from alumina and calcined diatomite with treatment in 1 mol/ιHCl solution at 24$0^{\circ}C$, was much larger than that of gibbsite and calcined diatomite shown previously, and that kaolinite and corundum minerals were coexistently formed under any hydrothermal treatment conditions. The plasticity of synthesized kaolinite from under 2 ${\mu}{\textrm}{m}$ alumina and calcined diatomite was very poor, and that of the synthesized kaolinite from raw diatomite and gibbsite gave higher than that of calcined diatomite and gibbsite.

• 대한치과보철학회지
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• 제43권5호
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• pp.684-693
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• 2005

Statement of problem: Ti-6Al-7Nb alloy is used instead of Ti-6Al-4V alloy that was known to have toxicity. Purpose: This study was performed to investigate the effect of electrolyte concentration on the surface characteristics of anodized and hydrothermally-treated Ti-6Al-7Nb alloy Materials and methods: Discs of Ti-6Al-7Nb alloy of 20 mm in diameter and 2 mm in thickness were polished sequentially from #300 to 1,000 SiC paper ultrasonically washed with acetone and distilled water for 5 min, and dried in an oven at $50^{\circ}C$ for 24 hours. Anodizing was performed at current density $30mA/cm^2$ up to 300 V in electrolyte solutions containing $\beta-glycerophosphate$ disodium salt hydrate $(\beta-GP)$ and calcium acetate (CA). Hydrothermal treatment was conducted by high pressure steam at $300^{\circ}C$ for 2 hours using a autoclave. All samples were soaked in the Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 30 days. Results and conclusion: The results obtained were summarized as follows: 1. After hydrothermal treatment, the precipitated HA crystals showed the dense fine needle shape. However, with increasing the concentration of electrolyte they showed the shape of thick and short rod. 2. When the dense fine needle shape crystals was appeared after hydrothermal treatment, the precipitation of HA crystals in Hanks' solution was highly accelerated. 3. The crystal structures of $TiO_2$ in anodic oxide film were composed of strong anatase peak and weak rutile peak as analyzed with thin-film X-ray diffractometery. 4. The Ca/P ratio of the precipitated HA layer was equivalent to that of HA crystal in Hanks' solution.

• 한국광물학회지
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• 제10권1호
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• pp.60-73
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• 1997

The talc of the Daeheung, Pyeongan, and Cheongdang (Shinyang) talc deposits in the Yesan-Gongju-Cheongyang area is a hydrothermal alteration product of serpentinite originated from ultramafic rocks. The mineral assemblages in alteration zones are: serpentine, serpentine-talc, talc, talc-chlorite, talc-phlogopite-chlorite, and talc-tremolite-chlorite. Chemical distributions in both the Al2O3-FeO-MgO system and the immobile elements suggest that the serpentine-talc and talc rocks are the reaction product of ultramafic rocks and silicic hydrothermal solution without addition of other granitic components, whereas chlorite-, phlogopite-, and tremolite-bearing rocks are the metasomatic alteration product of serpentinite by hydrothermal solution affected by granitic gneiss. Discontinuities in the immobile element ratios of mineral assemblages are due to changes in their mineralogy. The relative contents of Al2O3, TiO2, Zr in the talc-phlogopite-chlorite and talc-tremolite-chlorite rocks increase irregularly with increasing phlogopite, tremolite, and/or chlorite contents in contrast to other ore types. But the relative contents of Cr, Ni, and Co are uniform in all the mineral assemblages. Chemistry of each mineral assemblage formed by steatitization of serpentinite suggests that Cr, Co, Ni, MgO, and Fe2O3 are relatively immobile during the alteration, whereas SiO2, Al2O3, CaO, and K2O are highly increased. The contents of chlorite, phlogopite, and tremolite in each mineral assemblage might be controlled by addition of Al2O3, K2O, and CaO, respectively. The high contents of other elements than immobile elements in the altered rocks as compared with unaltered rocks indicate that a large amount of elements were introduced from hydrothermal solution up to about 8∼41% in total mass showing maximum value in the talc-phlogopite-chlorite rock.

• 자원환경지질
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• 제19권spc호
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• pp.43-52
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• 1986

Kaolin-pyrophyllite are locally abundant in the three hydrothermal areas at Yangsan-Tongnae area, Hadong-Sancheong area and Haenam area, deposits are originally composed of acidic volcanic rocks and anorthositic rocks in Hadong-Sancheong area. The clay deposits are formed in the near shallow depths environment through acid hydrothermal alteration. Hadong-Sancheong halloysite deposits are formed by alteration of anorthosite. These differences are mainly on the various country rocks, geological structure and properties of hydrothermal solutions. Country rock is mostly underlain by rhyolitic tuffaceous and anorthositic rocks and a large number of clay deposits were formed during volcanic activity through upper Cretaceous-lower Tertiary. Intrusive rocks is broadly distributed in this area and clay deposits are variable in shapelayer and funnel typed. Zonal pattern of mineral assemblage is as follows, Yangsan-Tongnae deposits-kaolinite, pyrophyllite, dumortierite, andalusite and sericite, Hadong-Sancheong-mostly halloysite, and Haenam-dickite, pyrophyllite, alunite and diaspore. The difference in the zonal pattern of altered rock is considered to depend on differences in the initial acidity of related hydrothermal solution, initial acidity was controlled by the oxygen fugacity.

• 한국세라믹학회지
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• 제34권7호
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• pp.747-757
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• 1997

ZSM-5 zeolite composite membranes have been synthesized from a silica sol solution containing TPABr as an organic template by the dip-coating and the pressurized-coating hydrothermal treatment techniques. The CO2 separation efficiency of synthesized composite membranes was also investigated. The permeation mechanism of CO2 through ZSM-5 membranses was the surface diffusion, and that of N2, O2, and He gases was Knudsen diffusion or activated diffusion depending on the synthetic method of membranes and the measurement temperature. The CO2/N2 separation factor of the membrane prepared by the dip-coating hydrothermal treatment was 2.5 at about 12$0^{\circ}C$, while the ZSM-5 composite membrane synthesized by the pressurized-coating hydrothermal treatment technique showed the CO2/N2 separation factor of 9.0 at room temperature higher than that ever reported in the literature.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.420-421
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• 2005

$LiMnPO_4$ particle were prepare by a hydrothermal reaction. The particles prepared by adding polyethylene glycol(PEG) and carbon to the starting reaction solution were fine crystalline in the range of 200-300nm. The discharge capacity of the sample as a lithium secondary battery was $25mAhg^{-1}$ at $0.04mAcm^{-2}$, larger than that of the sample prepared by the hydrothermal method without PEG and carbon.

• 한국결정성장학회지
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• 제1권1호
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• pp.60-65
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• 1991

The hydrothermal growth of $GaPO_{4}$ Single Crystals was carried out by the horizontal temperature gradient method. The most promising solvents for the crystal growth of $GaPO_{4}$ are $H_{3}PO_{4}$ and HCl solutions. Single crystals have been hydothermally grown at temperatures over the range $210-290^{\circ}C$ in these solutions with seed crystals. The glowth rates in HCl solution were higher than that for comparable conditions in $H_{3}PO_{4}$ solution. Morphologies of crystals grown at temperatures below $200^{\circ}C$ tended to be bounded by small major rhombohedral(10$\bar{1}$1) faces. In the temperature range from 200 to $430^{\circ}C$, the single crystals have morphologies bounded by prism (10$\bar{1}$0), small major rhombohedral(10$\bar{1}$1) and minor rhombohedral(01$\bar{1}$1) faces at the early stage, and grew with well developed basal(0001) faces by increasing the growth temperature.

• 대한치과보철학회지
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• 제43권3호
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• pp.363-378
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• 2005

Statement of problem. Hydroxyapatite(HA) coated titanium surfaces have not yet showed the reliable osseointegration in various conditions. Purpose. This study was aimed to investigate microstructures, chemical composition, and surface roughness of the surface coated by the hydrothermal method and to evaluate the effect of hydrothermal coating on the cell attachment, as well as cell proliferation. Material and Methods. Commercially pure(c.p.) titanium discs were used as substrates. The HA coating on c.p. titanium discs by hydrothermal method was performed in 0.12M HCl solution mixed with HA(group I) and 0.1M NaOH solution mixed with HA(group II). GroupⅠ was heated at 180 $^{\circ}C$ for 24, 48, and 72 hours. GroupⅡ was heated at 180 $^{\circ}C$ for 12, 24, and 36 hours. And the treated surfaces were evaluated by Scanning electron microscopy(SEM), Energy dispersive X-ray spectroscopy(EDS), X-ray photoelectron spectroscopy(XPS), X-ray diffraction method(XRD), Confocal laser scanning microscopy(CLSM). And SEM of fibroblast and 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) assay were used for cellular responses of the treated surfaces. Results. The color of surface changed in both groups after the hydrothermal process. SEM images showed that coating pattern was homogeneous in group II, while inhomogeneous in group I. H72 had rosette-like precipitates. The crystalline structure grew gradually in group II, according to extending treatment period. The long needle-like crystals were prominent in N36. Calcium(Ca) and phosphorus(P) were not detected in H24 and H48 in EDS. In all specimens of group II and H72, Ca was found. Ca and P were identified in all treated groups through the analysis of XPS, but they were amorphous. Surface roughness did not increase in both groups after hydrothermal treatment. The values of surface roughness were not significantly different between groups I and II. According to the SEM images of fibroblasts, cell attachments were oriented and spread well in both treated groups, while they were not in the control group. However, no substantial amount of difference was found between groups I and II. Conclusions. In this study during the hydrothermal process procedure, coating characteristics, including the HA precipitates, crystal growth, and crystalline phases, were more satisfactory in NaOH treated group than in HCl treated group. Still, the biological responses of the modified surface by this method were not fully understood for the two tested groups did not differ significantly. Therefore, more continuous research on the relationship between the surface features and cellular responses seems to be in need.